In FIG. 1, a current network architecture for the transport of media data streams is shown in which Media GateWays (MGW) 20, 21 transport a media payload/a media data stream between various sources and destinations, such as the payload transport nodes 30, 31, which could be also the payload sources and destinations. The control of the media data stream is handled by the Media Gateway Controllers 10, 11 (MGC) or other control nodes of the network. In the embodiment of FIG. 1, the dashed lines show the transport of control data whereas the solid lines show the transport of the media payload.
With the introduction of very high-capacity interfaces such as 1 GE (Gigabit Ethernet port) or 10 GE interfaces at the moment and with 40 GE or 100 GE in the future, the potential problem occurs that instead of the transport links, i.e. the connections between the media gateways, the media gateway or the IP network switch in a Software-Defined Network (SDN) is gradually becoming the network bottleneck.
The MGW can be located in wireline, 2G/3G mobile or IMS (IP Multimedia Subsystem)/VoIP (Voice over IP)/LTE (Long Term Evolution) networks
As a result of a congestion at the media gateway, the node will not be able to process new incoming traffic, will take longer to answer any requests meaning that the call or session setup time will increase to unacceptable levels. Furthermore, the ongoing traffic will be affected as the media gateway starts to lose packets belonging to ongoing calls/sessions.
WO 2010/034539 discloses a method for receiving a congestion indication for resources on a route to a target through a first network type. When a subsequent setup request for a call in the route is received, it is checked whether a congestion indication exists for the route. If yes, the call is established on an alternative route through a second type network.
The existing congestion control mechanisms are focusing on congestions in the transport or signaling network. When the media gateway itself is congested, the affected media gateway will report back to the media gateway controller the lack of available resources and the percentage of congestion level. Based on the received information, the media gateway controller will avoid the selection of the congested media gateway following a selection algorithm that is influenced, among other factors, by the reported congestion level. Looking at the node congestion case, the media gateway reports an error message 510 over ITU-T H.248 protocol, which means that a received command is rejected due to a lack of common resources in the media gateway. The error text in the error descriptor includes the name or identity of the property, signal or event that represents a lacking of resources in the media gateway.
As a result the controlled media gateway and the media gateway controller are not able to discern or pinpoint the reason of the congestion and the media gateway will process less traffic independent of the fact whether or not the source of the new traffic was a significant contributor to the congestion in the node.
With the high capacity interfaces mentioned above of 1-10 GE with a higher capacity being expected in the future, it is less and less unlikely that an interface will become congested before the node will be. As a consequence, the bottleneck is moved from the transport network into the node that handles the transport.
In the existing solutions the focus is to protect the media gateway and the ongoing calls or sessions of media data streams for a certain period of time or to restrict the volume of traffic handled by the media gateway with the hope that the peak period will pass and that the traffic volume in the media data stream will decrease.
In most of the cases, however, the source of the congestion will continue to generate a high volume of traffic. This gradually leads to similar congestion situations in the other media gateways connected to the same source and the involved additional network nodes become congested as well. The media gateway controller's selection algorithm will not be able to cope with the situation and will begin to act as if none of the media gateways were congested: each media gateway from the group will receive an equal amount of new calls as there are no alternative destinations available. This leads to a network with reduced call processing capacity, with a high number of unsuccessful call/session attempts, with significantly increased call/session setup times, causing discontent of the end-users and complaints to the operator's customer service.
Accordingly, a need exists to avoid at least some of the above-mentioned problems and to optimize the forwarding of media data streams at congested forwarding elements.